1. Field of the Invention
The present invention relates to an apparatus and method for driving an image display device using a DMD, and more particularly, to an apparatus and method for driving an image display device using a DMD, in which a margin of a light mute region at a color change can be minimized by correctly detecting a timing in a change of a color filter during rotation of a color wheel employed in a projection-type image display device using a DMD.
2. Description of the Related Art
Recently, with the advance of information industries, image display devices capable of displaying a large-sized image are in great demand. One of them is a projection-type image display device. A digital light processing (DLP) projector and a DLP projection TV using a digital micromirror device (DMD) are spotlighted.
FIGS. 1 and 2 are views of a color wheel used in a related art DLP projector or DLP projection TV.
Referring to FIGS. 1 and 2, the color wheel 10 has two RGB color filters. The color wheel 10 rotates at a predetermined frequency and separates a white light incident from a lamp 20 into R, G and B colors. Then, the R, G and B colors are provided to a DMD 30.
Light incident to the DMD 30 through the color wheel 10 is selectively reflected to a projection lens or a light absorber by a plurality of micromirrors included in the DMD 30, such that an image is displayed on a screen.
As the color wheel 10 rotates, a timing of R, G and B color change occurring when passing through the RGB color filters must be synchronized with a driving signal of the micromirror, which is supplied to the DMD 30.
For this purpose, an index mark 12 is provided at a central cylinder and indicates a rotation reference position of the color wheel 10.
Accordingly, during the rotation of the color wheel 10, an optical sensor detects the index mark 12 and checks whether or not the color wheel 10 rotates at a constant speed.
Meanwhile, since one index mark 12 is used to check the rotation state of the color wheel 10, it is impossible to accurately know the timing in a change of the color filter (boundary positions of the R, G and B color filters).
Therefore, the timing in the change of the color filter is estimated through an arithmetic operation, based on the position of the index mark 12. Then, the light is turned off during a margin period before and after the estimated timing, so that a light mute region cannot be displayed.
At this point, the light can be turned off by reflecting all incident light to the light absorber by setting an angle of the micromirror of the DMD 30 to −10° C.
FIG. 3 illustrates a phase relationship between a change of the R, G and B color filters and R, G and B images actually displayed during the rotation of the related art color wheel.
FIG. 3(A) illustrates a phase change of the R, G and B color filters during the rotation of the color wheel, and FIG. 3(B) illustrates a phase of the R, G and B images actually displayed.
As shown in FIG. 3(B), a predetermined margin period M exists before and after time points when the R, G and B color filters change.
The margin period M is set to be sufficiently large based on the arithmetic operation with reference to the index mark 12. The reason is that it is impossible to accurately know the timing in the change of the color filters.
However, when the margin period M is set to be large, the light is not displayed during that period. Therefore, the use efficiency of the light is degraded and thus an entire brightness of the DLP projector or the DLP projection TV is lowered.
Also, the unused light is scattered and is changed into heat within the DLP system or projected on a screen, thus generating noise.